JPH0788770B2 - Exhaust muffler for automobile - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust muffler for an automobile, and more particularly to a muffler capable of switching exhaust resistance, and by changing the exhaust resistance of the noise canceller, it is possible to respond to operating conditions. The present invention relates to an exhaust muffler for an automobile, which has improved noise reduction performance or engine output performance.

2. Description of the Related Art As an exhaust silencer of this type, for example, JP-A-62-12
Conventionally, there is one disclosed in Japanese Patent No. 6217.

In such a conventional exhaust silencer, the silencer performance of the silencer, that is, the exhaust resistance of the silencer can be switched via a switching valve in accordance with the engine speed or the load.
When driving in urban areas where the engine load is relatively small, the exhaust resistance is increased (valve closed) to widen the area, and the noise reduction effect is increased. On the contrary, during high-speed driving that requires a large engine load or during rapid acceleration, The engine output performance is improved by widening the area where exhaust resistance is reduced (valve open).

Problems to be Solved by the Invention However, in such a conventional exhaust silencer,
By simply changing the switching point of the exhaust resistance between when the engine is under heavy load and when the engine is under low load, it is possible to select whether to emphasize the muffling or to emphasize the output.

However, when exhaust resistance is switched depending on the engine load and engine speed, even if the muffling performance or engine output performance depending on the driving situation is improved, the muffled sound in the vehicle interior caused by the exhaust discharge sound is suppressed. No measures are taken, and the muffled noise is increased depending on the setting at the time of switching the exhaust resistance.

That is, in a V-type 6-cylinder engine having different lengths from each cylinder to the one-sided three-cylinder and the confluence part of each exhaust manifold of the remaining three cylinders, the exhaust discharge sound energy of the silencer is shown by the solid line in FIG. As shown, the third-order component of the engine rotation appears significantly during engine speed-2000 rpm when the valve is open, during acceleration when the engine load increases.
At the time of deceleration where the engine load becomes smaller, the exhaust phase shift was caused by the difference in the lengths of the exhaust manifolds of the three cylinders and the remaining three cylinders to the junction 1.
It has been confirmed that the 5th order component appears largely near 3000 to 4000 rpm with the valve open.

In addition, at the time of switching the exhaust resistance, the engine speed is set to 20 in an actual vehicle in order to improve the output performance of the engine.
It is set to 00-3000 rpm.

Therefore, the switching point of the exhaust resistance and the engine speed region where the exhaust discharge sound energy is increased overlap with each other, and the switching valve is opened in the rotation speed region where the exhaust discharge sound energy is increased. At some point, the energy is exhausted in a large state.

On the other hand, it is known that the muffled sound in the passenger compartment is generated by the resonance of the input vibration in the indoor cavity. Affect.

For example, if the vehicle front-rear direction dimension (l) is 1.9 m,
The vehicle longitudinal resonance frequency (γ) in the passenger compartment is γ = c / l × 1
From / 2 (c: sound velocity ≈ 34 m / S), γ = 89.5 Hz, and if this is converted to the engine speed, the 1.5th component of engine speed will be N
_1.5 = 60 / n × f = 60 / 1.5 × 89.5 = 3580 _(rpm) and N ₃ = 60/3 × 89.5 = 1790 _{(rpm) in the third} component.

However, as shown in FIG. 6, when the valve is open,
Rotational speed of the third-order component that resonates as the above muffled sound during acceleration
The N ₃ region is matched with the region where the exhaust discharge sound energy increases,
At the time of deceleration, the rotational speed N _1.5 region of the 1.5th order component coincides with the exhaust emission sound energy increase region.

Therefore, when the muffled sound peak point in the N ₃ region during acceleration and the muffled sound peak point in the N _1.5 region during deceleration are passed through in this way, the muffled sound in the passenger compartment is significantly increased, and the quietness in the passenger compartment is improved. There was a problem that it was damaged.

Therefore, an object of the present invention is to provide an exhaust muffler for a vehicle, which can significantly reduce the muffled noise in the vehicle compartment while satisfying the muffling performance and the output performance of the engine according to the driving situation.

Means for Solving the Problems In order to achieve such an object, the present invention is a 2M cylinder engine (M = C) in which the distance from each cylinder to the exhaust manifold merging portion of all cylinders is different between the M cylinder and the remaining M cylinder. 1,2,
3)), a silencer whose exhaust resistance is switched via a switching valve, and means for detecting the engine load and engine speed of the vehicle, respectively, and the engine load and / or engine speed detected by the means. According to the above, the switching muffler is closed at the low load or low rotation side of the engine to improve the muffling performance, and is opened at the high load or high rotation side to improve the output performance of the engine. In the case where the engine load is large, the switching valve opening / closing switching point is set near the side where the engine speed is higher than the M-th engine speed corresponding to the resonance frequency in the vehicle front-rear direction in the vehicle interior, and In the case of a small value, it is configured by setting it in the vicinity of the side where the engine speed of the M / 2 order corresponding to the above resonance frequency is higher.

In the exhaust silencer of the present invention having the above-described configuration, when the switching valve is opened and closed, when the engine load is large, it is larger than the M-th engine speed corresponding to the resonance frequency in the vehicle longitudinal direction in the vehicle interior. Since the switching valve is kept closed at the engine speed corresponding to the front-rear resonance frequency, the exhaust muffling energy that resonates in the vehicle front-rear direction in the vehicle interior from the silencer is set. It is possible to prevent the increasing component from being generated.

Similarly, even when the engine load is small, the switching time point of the switching valve corresponds to the resonance frequency in the vehicle longitudinal direction in the vehicle interior.
It is set on the side that becomes higher than the engine speed of M / 2 order,
At this point, it is possible to prevent the switching valve from being closed to generate an increased component of exhaust emission sound energy that resonates in the vehicle interior.

Therefore, the muffled sound in the vehicle compartment is significantly reduced as the increased components of the exhaust emission sound resonated in the vehicle front-rear direction in the vehicle compartment can be reduced.

Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

That is, FIG. 1 shows an exhaust muffler 10 for an automobile showing an embodiment of the present invention, in which 12 is an engine, 14 is an exhaust pipe, and 16 is the exhaust pipe.
It is a silencer provided at the end of 14.

In the present embodiment, the engine 12 is a so-called V-type 6-cylinder engine in which three cylinders are arranged in a V-shape.
In the cylinder engine 12, since the number of cylinders is 4 cycles and 6 cylinders, the explosion occurs three times per one revolution of the crankshaft, and the exhaust emission sound corresponding to this is generated.

The exhaust pipe 14 is connected to the exhaust manifolds 18 and 18a extending from each cylinder of the engine 12 in pairs of three cylinders on each side, and exhausts exhaust gas generated in each cylinder to the outside through the silencer 16. 20 is a contact converter.

As shown in FIG. 2, the silencer 16 has a pipe 24 for introducing exhaust gas into a casing 22 which is closed with an airtight structure.
And two discharge punching pipes 26, 28 are provided, the exhaust pipe 14 is connected to the introducing pipe 24, and the discharge punching pipes 26, 28 have first and second tail tubes 30, respectively. 32 is connected.

The first tail tube 30 is provided with a switching valve 34 that opens and closes the tube.
When the valve is switched to the open state via, the exhaust resistance is reduced to increase the output of the engine, and when the switching valve 34 is switched to the closed state, the exhaust resistance is increased to increase the muffling effect.

The switching valve 34 is opened and closed based on the engine load and the engine speed.

Therefore, the accelerator pedal 38 is provided with an accelerator opening sensor 40 as an engine load detecting means, and the engine 12 is provided with a rotation speed sensor 42 as an engine rotation speed detecting means. Each detection signal of the rotation speed sensor 42 is input to the controller 44, and the controller 44 determines the switching time point of the switching valve 34.

Based on a signal from the accelerator opening sensor 40, it is determined whether the vehicle is in an accelerating state or a decelerating state, and the acceleration / deceleration determination time is set to the accelerator opening ½ in this embodiment.

On the other hand, the signal from the rotation speed sensor 42 determines the switching time point of the switching valve 34 in the acceleration state and the deceleration state of the vehicle.

That is, the switching of the switching valve 34 depending on the engine speed takes into account the balance between the increase region of the noise reduction effect due to the valve closing and the increase region of the engine output due to the valve opening, and then the muffled noise inside the vehicle, that is, the vehicle inside the vehicle. It is determined based on the longitudinal resonance frequency γ.

The resonance frequency γ is determined by the vehicle front-rear direction dimension 1 in the passenger compartment, and is expressed as a standing wave having the dimension 1 as a half wavelength as shown in FIG.

Therefore, the vehicle longitudinal frequency can be obtained as γ = C / l × 1/2 ... (C: sound velocity ≈340 m / S). The constant 1/2 is a condition for the standing number of a half wavelength.

Here, when γ is obtained from the actual vehicle size, l = 1.
When it is set to 9 m, γ = 340 ^{m / s /} 1.9 ^{m ×} 1/2 = 89.5 Nz from the formula.

Next, the engine speed when the resonance frequency γ matches the order component of the engine is obtained.

The order component of the engine means here the number of impact sounds (exhaust sound) generated in the explosion stroke of the engine input to the exhaust pipe 14 per one revolution of the engine, and the third order component per revolution of the engine. It occurs 3 times, and in the 1.5th component, it occurs 1.5 times per rotation due to the length of the left and right exhaust manifolds 18 and 18a.

It has also been confirmed that the above-mentioned third-order component appears when the engine load is large, such as during acceleration, and the above-mentioned third-order component appears when the engine load is small, such as during deceleration.

Therefore, the engine speed N ₃ that matches the resonance frequency γ of the third-order component is N ₃ = 60 / n × γ = 60/3 × 89.5 = 1790 _(rpm) , and The number of revolutions N _1.5 that coincides with γ is N _1.5 = 60/15 × 89.5 = 3580 _(rpm) , and the peak point of the muffled noise in the passenger compartment appears at each of these numbers of revolutions N ₃ and N _1.5 .

However, as shown in FIG. 6, in the open state of the switching valve 34 at the time of acceleration, the exhaust emission sound energy of the third-order component is present in the rotational speed region (up to 2000 rpm) overlapping the rotational speed of N ₃ described above. When the switching valve 34 opens greatly during deceleration, the exhaust discharge sound energy of the 1.5th order component largely appears in the rotational speed region overlapping the rotational speed of N _1.5 .

Therefore, during acceleration (accelerator opening of 1/2 or more), the third-order component muffled sound peak point appears in the rotation speed N ₃ region, and during deceleration (accelerator opening of 1/2 or less), the 1.5th-order component muffled If the switching valves 34 are kept open in the engine speed N _1.5 region where the sound peak point appears, the increased exhaust discharge sound energy affects the vehicle interior, leading to an increase in muffled sound. .

Therefore, in the engine speed region in which the third-order component and the 1.5th-order component appear, it is necessary to particularly close the switching valve 34 to reduce the exhaust emission sound energy in the third-order component and the 1.5th-order component.

In FIG. 6, the solid line shows the sound pressure level characteristic when the valve is open, and the broken line shows the sound pressure level characteristic when the valve is closed.

Therefore, in the present embodiment, in consideration of the above-described necessary region for the noise reduction effect, the required region for the engine output, the increased region of the exhaust emission sound energy that affects the muffled noise in the vehicle interior, and the like,
The switching region of the switching valve 34 is set as shown in FIG.

That is, in the switching region diagram of FIG. 3, the horizontal axis represents the engine speed and the vertical axis represents the accelerator opening. In the accelerator opening direction, the accelerator opening for determining acceleration / deceleration state is shown.
A switching boundary is set at the 1/2 part, and a switching boundary is set at the engine speed n _A (during acceleration) and engine speed n _B (during deceleration).

The rotation speed n _A is calculated as a safety margin from the rotation speed (N ₃ = 1790 rpm) corresponding to the muffled sound peak point of the third-order component.
00rpm large value, for example, is set to n _A = 2500 rpm, and the rotational speed n _B is the rotational speed corresponding to the muffled sound peak point of 1.5-order component (N _1.5 = 3580rpm) n anticipation safety margin as well from _B = Set to 4600 rpm.

In addition, the width of each safety margin may be set as appropriate in consideration of a region necessary for increasing engine output during acceleration, a region that is significantly affected by muffled noise, a region where exhaust emission sound energy increases, and the like. Further, it may be appropriately set in consideration of a region requiring the exhaust noise suppression effect at the time of deceleration, a region in which the exhaust discharge sound energy increases, and the like.

By the way, the switching boundaries set respectively in the accelerator opening direction and the engine speed direction in FIG. 3 are a switching boundary line a from the closed to open direction indicated by the solid line in the figure and an open to closed direction indicated by the broken line in the figure. A hysteresis is provided between the switching boundary line b and the switching boundary line b, and the hysteresis width is set to about 100 rpm in the engine speed direction.

With the above-described configuration, in the vehicle exhaust muffler 10 of the present embodiment, as shown in FIG. 4, when the vehicle is accelerated to an accelerator opening of 1/2 or more, the resonance frequency γ in the vehicle longitudinal direction becomes equal to the resonance frequency γ. Since the rotation speed n _A, which is higher than the corresponding third engine rotation speed N ₃ by the predetermined rotation speed, is set as the switching time point of the switching valve 34, the switching valve 34 is closed in the N ₃ region. The third component of the exhaust emission sound energy shown in FIG. 6 can be suppressed to a low level.

Therefore, the exhaust discharge sound is prevented from being greatly affected in the vehicle interior in the above N ₃ region, and as shown by the muffled sound / sound pressure level characteristics in FIG. 5, the third-order component peak region shown by the solid line is one point. As shown by the chain line, the noise that resonates in the vehicle front-rear direction in the vehicle interior is significantly reduced, and the quietness in the vehicle interior can be significantly improved.

On the other hand, at the time of deceleration of the vehicle where the accelerator opening is 1/2 or less, the engine speed n _B greater than the _1.5th engine speed N _1.5 corresponding to the vehicle longitudinal resonance frequency γ by a predetermined engine speed n _B.
Since was the switching point of the switching valve 34, in the N _1.5 area for switching valve 34 is closed, it is possible to suppress the 1.5-order component of the exhaust discharge sound energy low.

Therefore, the exhaust emission noise is prevented from being greatly influenced in the vehicle interior in the N _1.5 region, and the 1.5th order component peak region shown by the broken line as shown in FIG. 5 is reduced as shown by the chain double-dashed line. , It is possible to significantly reduce the muffled noise in the passenger compartment and improve the quietness in the passenger compartment.

By the way, in the present embodiment, it is of course possible to reduce the muffled noise as described above, and at the time of acceleration (accelerator opening 1/2 or more), the switching time of the switching valve 34 is on the low rotation speed side. Since it is set to, it is possible to set a wide range of the engine output increase and at the time of deceleration (accelerator opening 1 /
(2 or less), the switching time point is set to the high rotation speed side, so that the range of increasing the muffling effect can be set wide.

Further, in the present embodiment, when switching the switching valve 34, a hysteresis is provided between the switching boundary line a from the closed direction to the opening direction and the switching boundary line b from the open direction to the closing direction. It is possible to prevent hunting and prevent frequent engine output fluctuations.

In this embodiment, the case where the accelerator opening sensor 40 is used as the engine load detecting means is shown, but the negative pressure sensor for detecting the suction negative pressure of the engine is not limited to this,
The engine load may be detected by using a temperature sensor or the like provided in the exhaust passage.

In this embodiment, the boundary point for determining the acceleration state and the deceleration state is set to the accelerator opening 1/2, but the acceleration / deceleration boundary point may be set appropriately according to various engine performances. it can.

Furthermore, the engine used is not limited to the V-type 6-cylinder engine, and the 2M cylinders (M = 1,2,3 ...) having different lengths of the exhaust manifold for the M cylinders and the exhaust manifolds for the remaining M cylinders are used. Needless to say, the present invention can be applied to any engine.

As described above, in the vehicle exhaust muffler of the present invention, when the switching valve of the muffler is switched, when the engine addition is large, the Mth order corresponding to the longitudinal resonance frequency of the vehicle in the passenger compartment is set. Since it is set in the vicinity of the side where the engine speed is higher than (M = 1,2,3 ...), the valve is closed in the region where the exhaust gas discharge noise increases that appears overlapping with the M-th engine speed region. In this state, the exhaust emission sound energy of the M-order component can be significantly reduced, so that the muffled sound in the vehicle compartment can be significantly reduced.

Further, when the engine load is small, the switching time point is set in the vicinity of the side that becomes higher than the M / 2-order engine speed corresponding to the resonance frequency. Exhaust discharge noise M / that appears when wrapped
Even if the energy of the secondary component is greatly reduced by closing the valve, the muffled noise can be significantly reduced, and in combination with the muffled noise reduction when the engine load is large, the quietness of the vehicle interior is significantly improved. be able to.

Furthermore, since the M-order engine speed is relatively low,
Along with this, the switching valve also switches to a low speed range,
It is possible to increase the range of engine output by opening the valve to improve the acceleration performance, and since the engine speed of the M / 2 order above is relatively high, the range of increasing the noise reduction effect by closing the valve is widened. It has various excellent effects that the noise prevention performance can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view showing an embodiment of a silencer used in the present invention, and FIG. 3 is a resonance of vibration causing a muffled sound. FIG. 4 is an explanatory diagram showing a state, FIG. 4 is a switching region diagram of a switching valve set in the present invention, FIG. 5 is a sound pressure level characteristic diagram of muffled noise with respect to engine speed, and FIG. 6 is exhaust gas discharge with respect to engine speed. It is a sound pressure level characteristic diagram of a sound. 10 …… Exhaust silencer, 12 …… Engine, 14 …… Exhaust pipe,
16 …… Silencer, 18,18a …… Exhaust manifold, 34
...... Switching valve, 38 …… accelerator pedal, 40 …… accelerator opening sensor (engine load detection means), 42 …… speed sensor (engine speed detection means).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 62-126217 (JP, A) actual open 62-156111 (JP, U) actual open 62-169216 (JP, U) actual open 62- 183013 (JP, U)

Claims (1)

[Claims] 1. A 2M cylinder engine (M = 1, 2, 3, ...) In which the distance from each cylinder to the exhaust manifold merging portion for all cylinders differs between the M cylinder and the remaining M cylinders, and through a switching valve. And a means for detecting the engine load and the engine speed of the vehicle, respectively, and the switching valve according to the engine load and / or the engine speed detected by the means. Closed on the low load or low rotation side to improve the noise reduction performance,
In addition, in an automobile exhaust muffler that opens at a high load or high rotation side to improve the output performance of the engine, when the switching valve is opened or closed, when the engine load is large, resonance in the vehicle longitudinal direction in the vehicle interior occurs. M corresponding to the frequency
Set near the side where the engine speed is higher than the next engine speed,
Further, when the engine load is small, the exhaust silencer for a vehicle is set in the vicinity of a side where the engine speed of the M / 2 order corresponding to the resonance frequency is higher than the engine speed.